design and deployment of a mule plugin split-parallel ... with investigating component fitment using...

EVS27 International Battery, Hybrid and Fuel Cell Electric Vehicle Symposium 1

EVS27 Symposium

Barcelona, Spain, November 17-20, 2013

Design and Deployment of a Mule Plugin Split-Parallel

Chevrolet Malibu: Integration

Jon Nibert1, Laura Nash, Josh King, Zachariah Chambers

2, Marc Herniter,

1Rose-Hulman Institute of Technology 5500 Wabash Avenue CM189 Terre Haute, IN 47803

[email protected]

2RHIT Faculty Advisers

Short Abstract

As a selected participant in the EcoCAR2: Plugging In to the Future competition, headline sponsored by

General Motors and the US Department of Energy, the Rose-Hulman team has completed the second year

of a three year design cycle. This paper focuses on the mechanical integration of powertrain components

based on the year one design. The selected architecture, a plugin split-parallel, utilizes a GM LE9 2.4L

Flexfuel engine, a GM MHH eAssist 6-speed automatic transmission, a modified GM BAS and inverter, a

Remy HVH250 rear traction motor with Rinehart inverter, and custom A123 battery.

1 Introduction

Rose-Hulman Institute of Technology (RHIT) is an undergraduate focused college of engineering, science,

and mathematics located in Terre Haute, Indiana USA. RHIT has been participating in the General Motor (GM) and US Department of Energy (DoE) headline sponsored Advanced Vehicle Technology

Competitions (AVTCs) since 2004 when selected to join the Challenge-X competition. These AVTCs are

rigorous three year design sequences which challenge 15 North American universities and colleges to

design, produce, and validate a hybrid vehicle. These vehicles utilize alternative fuels to decrease

petroleum consumption and emissions production on a Well-to-Wheels basis without compromising consumer acceptability in performance, utility, and/or safety. The first year of the competition focuses on

vehicle system modelling; utilizing Matlab and Simulink to predict performance specifications in parallel

with investigating component fitment using Siemens NX 7.5. Year two culminates with the testing of a 60% buyoff mule vehicle which is then optimized and refined to 99% buyoff quality during year three. For

the current AVTC EcoCAR2: Plugging In to the Future the vehicle platform is a 2013 Chevrolet Malibu.

A key team decision was to create a performance oriented vehicle as a market differentiator: the Malibu eco

sport. Modelling and simulation work performed during year one, presented in EVS27 paper titled

“Design of a Plugin Split-Parallel Chevrolet Malibu: Control Strategy Development”, within the constraints

of available GM or third party resources, indicated that a plugin split-parallel architecture would best meet the team and competition goals. The components selected are presented in Table 1 and high-level

architecture layout is presented in Figure 1.


Component Source

Engine GM LE9 2.4l four cylinder (using E85)

Transmission GM MHH 6-speed automatic with eAssist

Belt Electric Machine Modified GM BAS, Rinehart Inverter

Rear Traction Motor Remy HVH250p

Energy Storage System (ESS) A123 7m15s2p

Table 1: Selected Powertrain Components

Figure 1: High Level Vehicle Architecture


The control strategy has two primary operating modes: charge depleting and charge sustaining. In charge

depleting mode, the vehicle operates electrically, powered by the rear traction motor (HVH250). When the

Energy Storage System (ESS) drops to a threshold level, the vehicle switches to the front powertrain and operates traditionally, powered by the engine and transmission. The BAS will be employed during year

three as a refinement to enable start stop. To achieve the performance goal of the Malibu ecosport

, a high

throttle request from the driver over-rides the current mode and activates both the engine and the motor yielding power levels near 330 HP while still achieving a combined cycle fuel economy of 38 mpg when in

normal operating modes.

2 Component Layout

After spending year one and the ensuing summer exploring and verifying fitment, the finalized locations

are presented in Figure 2.

Figure 2: Powertrain Component Locations

3 FEA Analysis

EcoCAR2 competition rules require an FEA analysis of non-stock powertrain mounts to be performed to ensure crash worthiness. Static loads of 20g were applied longitudinally and laterally and a static load of

8g was applied vertically in succession to the ESS subframe (Figure 3: ESS Subframe Model) and the

HVH/Fuel Tank (HVH/FT) subframe (Figure 5: HVH/FT Subframe) which are new structural additions to

the vehicle. The same loading conditions were then applied to the brackets which mount the HVH250 to

its subframe (Figure 7 and Figure 8).

The ESS will be secured to the vehicle by mounting to an ESS subframe. The design material for the ESS Subframe is 1020 cold rolled steel. This readily available variant of both the 1020 tube steel (3/4” x ¾” x

1/8” wall thickness) and the 1020 flat bar (1.75”x 1/8” thick), that will be used to fabricate the ESS

subframe are listed as having a yield strength of 350 MPa. Other properties of 1020 cold rolled steel

include a poison’s ratio of 0.290, an ultimate tensile strength of 420MPa, a modulus of elasticity of 205

GPa and a density of 7.87 g/cc.

As shown in Figure 4: ESS Subframe FEA Results (Longitudinal), the highest stresses were observed in the

longitudinal direction which yielded a maximum value of 55 MPa.


Figure 3: ESS Subframe Model

Figure 4: ESS Subframe FEA Results (Longitudinal)

The HVH/FT subframe is also constructed using 1020 cold rolled rectangular steel tubing; one piece that measures 1 “ x 1.5“ x 1/8” and the other one 1” x 3” x 1/8”. The yield strength of the material is

350 MPa. The HVH250 traction motor and the fuel tank are mounted to the HVH/FT subframe using threaded standoffs which are shown in Figure 5: HVH/FT Subframe. The HVH/FT subframe was

modelled in NX NASTRAN using a beam model as shown on the left in HVH/FT Subframe FEA Results

(Longitudinal). The mesh used was a 1D Element Section which gives the user the ability to define the

cross section of each beam element. The element size used for the mesh was 10mm.

Formatted: Font: Bold


Figure 5: HVH/FT Subframe

Figure 6: HVH/FT Subframe FEA Results (Longitudinal)

The NX NASTRAN FEA results for the HVH/FT subframe show that the highest stresses seen are in the

longitudinal direction in the amount of 173.5 MPa. Since the yield strength of the material is 350 MPa, a value of 173.5 MPa meets the competition mandated Factor of Safety (FOS) of 2. Black circles on the left

in Figure 6: HVH/FT Subframe FEA Results, indicate the 4 points where fixed constraints were applied to

the beam model. These constraints simulate the points where the subframe will be welded to the vehicle.

The HVH250 front and back brackets will mount the HVH250 to the HVH/FT subframe. The material used to fabricate the HVH250 front bracket will be normalized 4140 Cr-Mo Steel (yield strength of 655 MPa).

The HVH250 rear bracket will be made using annelled 4140 Cr-Mo Steel which has a yield strength of 915 MPa.

Material properties for the HVH250 front bracket are given in Table 2: Normalized 4140 Cr-Mo Steel

Material Properties. Table 3: Annealed 4140 Cr-Mo Steel Properties gives material properties for the HVH250 rear mounting bracket.

Yield Strength Poisson’s ratio Ultimate Tensile Strength Density

655 MPa 0.28 1020 MPa 7.8 g/cm3

Table 2: Normalized 4140 Cr-Mo Steel Material Properties


Yield Strength Poisson’s ratio Ultimate Tensile Strength Density

915 MPa 0.28 1655 MPa 7.8 g/cm3

Table 3: Annealed 4140 Cr-Mo Steel Properties

The HVH250 front bracket is shown as a 3D model on the left in Figure 7: HVH250 Front Bracket Model

and FEA Lateral Loading Results. The highest stresses observed in the HVH250 front bracket occur in the

lateral case with a maximum value of 285 MPa. The HVH250 rear bracket is shown as a 3D model on the

left in Figure 8: HVH250 Rear Bracket Model and FEA Lateral Loading Results. The highest stresses

observed in the HVH250 rear bracket occur in the lateral case with a maximum value of 454 MPa. Both

brackets were modelled in NX7.5 and then meshed using a 3D tetrahedral mesh with an element size of

2mm for the front bracket and 1.5mm for the rear bracket.

Figure 7: HVH250 Front Bracket Model and FEA Lateral Loading Results

Figure 8: HVH250 Rear Bracket Model and FEA Lateral Loading Results




For the material properties given above, the safety factors are given below in Error! Reference source not

found.

Longitudinal Lateral Vertical

ESS Subframe 6.4 13.0 40.7

HVH/Fuel

Tank Subframe 2.0 10.0 3.6

HVH Front Bracket 3.6 2.3 10.4

HVH Rear Bracket 2.5 2.0 10.1

Table 4: Safety Factors

4 Integration Validation

The final step in the deployment of the mule vehicle was to validate the integration per the year one design,

noting any deviations. Presented in the figures below are the CAD as intended integration and the

associated in-vehicle validation photograph. Vehicle exterior is presented first followed by the engine and

under-body and concludes with the interior. Vehicle integration followed the CAD in all instances with the

exception of the GM BASS and front Rinehart invertor. A supplier issue resulted in the stock GM BAS not

being rewound which necessitated a last minute change in design. The stock 12V alternator was retained

and the DC/DC converter was used to step the 12V up to the 350V bus voltage to provide stationary charging as opposed to going from 350V down to 12V to power the hotel loads.


Figure 9: Integration Validation – Exterior


Figure 7: Integration Validation – Engine Bay and Underbody


Figure 8: Integration Validation – Interior

5 Conclusion

In conclusion, year 1 of the EcoCAR2 competition established the overall integration plan to be

implemented during year 2. During year two, the ESS and HVH/FT subframes were designed and analysed

to meet or exceed a safety factor of two for the prescribed loading conditions. Powertrain components

were integrated into the vehicle as design for all with the exception of the rewound BAS and inverter.

6 Future Work

Over the next year the team will refine the vehicle to go from a 60% buyoff mule to a 99% buyoff

showroom ready final product.

Acknowledgments

The authors would like to acknowledge Kristen de la Rosa, EcoCAR2 Program Director, Argonne National

Lab and Zach Pieri, EcoCAR2 Team Mentor, General Motors.

References

[1] EVS27, http://www.EVS27.org, accessed on 2013-01-06

[2] http://asm.matweb.com


Authors

Jon Nibert is an Electrical Systems Integration Engineer at Ford Motor Company in

Dearborn, Michigan. He has his B.S. in Computer Engineering and M.S. in Engineering

Management from Rose-Hulman Institute of Technology. Prior to joining Ford, Jon spent

4 years in the EcoCAR and EcoCAR2 Advanced Vehicle Technical Challenges, including

1.5 years as the Lead Electrical Engineer and 2 years as the Engineering Manager for the

project. His core focuses are in electrical architecture design and implementation, project

management, engineering process development, and systems engineering.

Rose-Hulman Institute of Technology (RHIT’05) alumnus Laura Nash was a senior

contributing member of the 2005 Challenge X team. Laura served as the battery research

team leader as the team worked to select a split train hybrid electric vehicle architecture for

the first year of the competition. After graduating and working in industry, Laura has

returned to RHIT for graduate school (RHIT ’14) and joined the 2nd

and 3rd

years of the

EcoCAR 2 competition. Laura is a graduate assistant for the team and works on vehicle

integration and optimization of the RHIT EcoCAR2 vehicle. Additionally, Laura serves as

the Energy Storage System (ESS) team lead; heading the FEA analysis, the assembly of the

ESS components, and co-leading any necessary component redesigns. Laura also works

closely with the mechanical team in the fabrication of vehicle systems along with the

removal/ installation of new components.

Josh King is a member of the Rose-Hulman Institute of Technology class of 2014 studying

to receive his BS in Mechanical Engineering. He is a two-year member of the Rose-Hulman EcoCAR2 team and acted as the Mechanical sub-team lead this past year. He has

worked at two internships dealing with the design, test, and product development of hybrid electric motors and has filed a patent on an oil cooling design through one of the

internships.

Zac Chambers has his BS and MS in Mechanical Engineering from Rose-Hulman Institute

of Technology and his PhD in Engineering Science and Mechanics from the University of

Tennessee, Knoxville. He has been on the ME faculty for Rose-Hulman since 2000 and

has worked with Marc Herniter as Mechanical Advisor for ChallengeX, EcoCAR, and now

EcoCAR2 racking up 9 years of experience in hybrid vehicle powertrain design and

execution. He additionally serves as the Program Director for the Advanced

Transportation System Program at Rose-Hulman.

Marc Herniter is a Professor at Rose-Hulman Institute of Technology (Ph.D., Electrical Engineering, University of Michigan, Ann Arbor, 1989); Dr. Herniter's primary research

interests are in the fields of modeling of complex systems, power electronics, hybrid vehicles, and alternative energy systems. He has worked on power electronic systems that

range in power levels from 1500 W to 200 KW. He is the author of several text books on

simulation software including PSpice, Multisim, and Matlab. He is currently the co-advisor

for the Rose-Hulman EcoCAR Hybrid-Electric vehicle team and the faculty supervisor of

Rose-Hulman’s Model-Based-Systems Design laboratory.

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